If you've only seen these in the mod menu then you should visit the config file as it has room to explain more :P

HudHints is always visible only when you're in the first vanilla HUD mode after you just turn it visible, the one where it shows key hints and tool/block descriptions, Pressing HUD key again hides those and pressing it again hides it entirely.

And for both HudHints and AltKey modes, toolbar info is shown for a few seconds when entering a cockpit.

There's no rebind option for AltKey mode, I'll add it to the to-do list :}

The rebind thing is in the bleeding edge version now :}
No idea when I'll update the main mod with all that =)

That's awesome ! I actually use Alt for down/crouch so you can see how it's less than optimal in my particular situation :D

Oh, hmm, I apparently forgot that alt's action is rebindable in game (lookaround), and I found some more places where I'm assuming alt is always that =) will be fixing those.